1. Field of the Invention
The present invention relates generally to rupturable pressure relief devices, and more particularly, to rupture disk assemblies which resist momentary pressure surges.
2. Description of the Prior Art
A variety of rupturable pressure relief devices have been developed and used heretofore. Commonly, such devices include a rupture member or disk which is of a particular strength whereby it ruptures when a predetermined fluid pressure is exerted thereon. The rupture disk is most often clamped between a pair of annular supporting members positioned in a pressure relief passageway or conduit connected to a vessel or system being protected from overpressure by the rupture disk.
While rupture disk assemblies comprised of a single rupture disk supported between supporting members are commonly utilized in particular applications, composite rupture disk assemblies comprised of two or more rupturable parts supported between supporting members are also commonly used. An example of a particular type of composite rupture disk assembly is comprised of a perforated rupture member formed of metal or other rigid material with a resilient sealing member positioned adjacent thereto. Other parts such as protection members for the resilient sealing member and additional perforated rupture members are often also included in the composite rupture disk assembly. A composite rupture disk assembly can include means for clamping the various parts together, and the entire assembly is adapted to be clamped between a pair of annular supporting members such as pipe flanges or the like.
The prior art rupture disk assemblies including single rupture disks or composite rupture disks have been highly commercially successful in a variety of overpressure protection applications. However, in applications where the vessel or system being protected is subject to momentary surges in pressure which exceed the predetermined rupture pressure of the rupture disk, less than desirable results often result. For example, when a pressurized liquid, such as liquefied petroleum gas, is transported in a tank truck or tank car, a sudden tank movement or stop causes the pressurized liquid to move within the tank which in turn causes a momentary surge in pressure within the tank. When a heretofore utilized rupture disk assembly is subjected to such a pressure surge and the surge causes a momentarily overpressure condition to be exerted thereon, the rupture disk assembly ruptures even though pressure relief from the vessel or system being protected is not required.
Thus, there is a need for a rupture disk assembly which will resist rupture when an overpressure condition is momentarily caused by a momentary pressure surge within a vessel or system being protected, but when an overpressure condition is reached slowly, the rupture disk assembly ruptures and provides needed pressure relief.